@tomy I never had such problems.
Are you sure it isn't something with your system?
"If they wanted to fix, they could have done it so far" - if they didn't have such problems (like me) and nobody reported those how should they know they have to fix them? If you have problems with software you should report them - this is how it works. If you encounter a bug in Qt you report it instead of waiting for Qt developers to detect and fix it by themselves. Many bugs only occur under specific conditions, so you cannot expect developers to detect all bugs by themselves.

@tomy If those applications do not start then you should check in Task Manager whether they are already running: sometimes an application hangs and if you try to start it again it detect that it is already running (there is a process) and does nothing.